diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
index 19370f62b..4893baeea 100755
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -1073,7 +1073,7 @@ class YoutubeDL(object):
                 '*=': lambda attr, value: value in attr,
             }
             str_operator_rex = re.compile(r'''(?x)
-                \s*(?P<key>ext|acodec|vcodec|container|protocol|format_id)
+                \s*(?P<key>[a-zA-Z0-9._-]+)
                 \s*(?P<negation>!\s*)?(?P<op>%s)(?P<none_inclusive>\s*\?)?
                 \s*(?P<value>[a-zA-Z0-9._-]+)
                 \s*$